[stdlib] Clarify variable name in UTF8
[stdlib] Clarify variable name in UTF8

_atEnd was confusing because it did not mean 'at the end of the sequence', because of buffering.
calebd/swift,hughbe/swift,tkremenek/swift,jtbandes/swift,bitjammer/swift,natecook1000/swift,rudkx/swift,austinzheng/swift,gottesmm/swift,hooman/swift,felix91gr/swift,gregomni/swift,bitjammer/swift,zisko/swift,KrishMunot/swift,gribozavr/swift,xedin/swift,devincoughlin/swift,ken0nek/swift,practicalswift/swift,modocache/swift,allevato/swift,xwu/swift,gmilos/swift,kstaring/swift,lorentey/swift,hooman/swift,gregomni/swift,therealbnut/swift,kperryua/swift,xedin/swift,jckarter/swift,lorentey/swift,ken0nek/swift,bitjammer/swift,stephentyrone/swift,airspeedswift/swift,lorentey/swift,ben-ng/swift,IngmarStein/swift,atrick/swift,apple/swift,CodaFi/swift,xwu/swift,gmilos/swift,shahmishal/swift,roambotics/swift,jopamer/swift,stephentyrone/swift,tjw/swift,nathawes/swift,brentdax/swift,tinysun212/swift-windows,gribozavr/swift,kperryua/swift,KrishMunot/swift,danielmartin/swift,ahoppen/swift,benlangmuir/swift,bitjammer/swift,ahoppen/swift,manavgabhawala/swift,jopamer/swift,roambotics/swift,aschwaighofer/swift,return/swift,sschiau/swift,parkera/swift,gribozavr/swift,atrick/swift,tardieu/swift,modocache/swift,swiftix/swift,apple/swift,xedin/swift,kperryua/swift,IngmarStein/swift,airspeedswift/swift,jopamer/swift,jtbandes/swift,therealbnut/swift,austinzheng/swift,swiftix/swift,OscarSwanros/swift,airspeedswift/swift,deyton/swift,xwu/swift,therealbnut/swift,alblue/swift,rudkx/swift,frootloops/swift,KrishMunot/swift,tkremenek/swift,gribozavr/swift,gregomni/swift,Jnosh/swift,calebd/swift,alblue/swift,benlangmuir/swift,jmgc/swift,JGiola/swift,uasys/swift,jckarter/swift,harlanhaskins/swift,natecook1000/swift,SwiftAndroid/swift,OscarSwanros/swift,Jnosh/swift,jmgc/swift,alblue/swift,djwbrown/swift,natecook1000/swift,dreamsxin/swift,karwa/swift,shahmishal/swift,djwbrown/swift,glessard/swift,harlanhaskins/swift,jmgc/swift,bitjammer/swift,russbishop/swift,russbishop/swift,ken0nek/swift,sschiau/swift,kstaring/swift,gribozavr/swift,practicalswift/swift,russbishop/swift,codestergit/swift,lorentey/swift,dduan/swift,Jnosh/swift,uasys/swift,tinysun212/swift-windows,danielmartin/swift,CodaFi/swift,harlanhaskins/swift,brentdax/swift,dreamsxin/swift,devincoughlin/swift,uasys/swift,JaSpa/swift,glessard/swift,codestergit/swift,KrishMunot/swift,KrishMunot/swift,Jnosh/swift,frootloops/swift,austinzheng/swift,shahmishal/swift,allevato/swift,ahoppen/swift,devincoughlin/swift,JaSpa/swift,benlangmuir/swift,airspeedswift/swift,xedin/swift,zisko/swift,jmgc/swift,glessard/swift,rudkx/swift,return/swift,gottesmm/swift,atrick/swift,uasys/swift,arvedviehweger/swift,felix91gr/swift,dduan/swift,tkremenek/swift,modocache/swift,tardieu/swift,modocache/swift,xedin/swift,deyton/swift,frootloops/swift,JaSpa/swift,gottesmm/swift,tjw/swift,shajrawi/swift,parkera/swift,OscarSwanros/swift,jtbandes/swift,gmilos/swift,karwa/swift,ben-ng/swift,parkera/swift,alblue/swift,OscarSwanros/swift,parkera/swift,frootloops/swift,calebd/swift,swiftix/swift,johnno1962d/swift,xwu/swift,hughbe/swift,tardieu/swift,shajrawi/swift,jtbandes/swift,parkera/swift,russbishop/swift,huonw/swift,devincoughlin/swift,karwa/swift,SwiftAndroid/swift,allevato/swift,modocache/swift,nathawes/swift,JaSpa/swift,CodaFi/swift,ben-ng/swift,Jnosh/swift,jckarter/swift,hooman/swift,manavgabhawala/swift,zisko/swift,ahoppen/swift,IngmarStein/swift,milseman/swift,harlanhaskins/swift,devincoughlin/swift,manavgabhawala/swift,shahmishal/swift,kstaring/swift,kperryua/swift,jtbandes/swift,gregomni/swift,amraboelela/swift,johnno1962d/swift,arvedviehweger/swift,djwbrown/swift,milseman/swift,SwiftAndroid/swift,practicalswift/swift,aschwaighofer/swift,gregomni/swift,deyton/swift,tkremenek/swift,arvedviehweger/swift,uasys/swift,tkremenek/swift,lorentey/swift,swiftix/swift,apple/swift,danielmartin/swift,danielmartin/swift,djwbrown/swift,brentdax/swift,russbishop/swift,roambotics/swift,JGiola/swift,SwiftAndroid/swift,airspeedswift/swift,SwiftAndroid/swift,deyton/swift,jopamer/swift,manavgabhawala/swift,IngmarStein/swift,milseman/swift,johnno1962d/swift,aschwaighofer/swift,jckarter/swift,amraboelela/swift,OscarSwanros/swift,karwa/swift,practicalswift/swift,lorentey/swift,stephentyrone/swift,Jnosh/swift,deyton/swift,johnno1962d/swift,dduan/swift,xedin/swift,practicalswift/swift,xedin/swift,apple/swift,alblue/swift,modocache/swift,arvedviehweger/swift,rudkx/swift,huonw/swift,hughbe/swift,airspeedswift/swift,shahmishal/swift,IngmarStein/swift,modocache/swift,johnno1962d/swift,bitjammer/swift,jopamer/swift,huonw/swift,ben-ng/swift,OscarSwanros/swift,rudkx/swift,jckarter/swift,tjw/swift,ben-ng/swift,karwa/swift,gottesmm/swift,arvedviehweger/swift,practicalswift/swift,xwu/swift,calebd/swift,russbishop/swift,ken0nek/swift,harlanhaskins/swift,allevato/swift,deyton/swift,felix91gr/swift,jopamer/swift,gottesmm/swift,shajrawi/swift,apple/swift,huonw/swift,sschiau/swift,calebd/swift,johnno1962d/swift,tinysun212/swift-windows,shajrawi/swift,roambotics/swift,sschiau/swift,aschwaighofer/swift,nathawes/swift,russbishop/swift,gmilos/swift,jopamer/swift,alblue/swift,tardieu/swift,brentdax/swift,lorentey/swift,glessard/swift,kstaring/swift,brentdax/swift,shahmishal/swift,therealbnut/swift,rudkx/swift,codestergit/swift,stephentyrone/swift,danielmartin/swift,lorentey/swift,tkremenek/swift,danielmartin/swift,milseman/swift,amraboelela/swift,tjw/swift,atrick/swift,calebd/swift,xwu/swift,shajrawi/swift,therealbnut/swift,allevato/swift,shajrawi/swift,djwbrown/swift,sschiau/swift,sschiau/swift,benlangmuir/swift,return/swift,tjw/swift,JaSpa/swift,aschwaighofer/swift,swiftix/swift,kstaring/swift,tardieu/swift,arvedviehweger/swift,return/swift,kperryua/swift,gottesmm/swift,karwa/swift,karwa/swift,hooman/swift,xwu/swift,huonw/swift,roambotics/swift,gmilos/swift,hooman/swift,frootloops/swift,JGiola/swift,IngmarStein/swift,jtbandes/swift,arvedviehweger/swift,airspeedswift/swift,stephentyrone/swift,atrick/swift,jmgc/swift,codestergit/swift,calebd/swift,SwiftAndroid/swift,milseman/swift,tjw/swift,JGiola/swift,hooman/swift,atrick/swift,CodaFi/swift,therealbnut/swift,JGiola/swift,alblue/swift,uasys/swift,devincoughlin/swift,amraboelela/swift,dduan/swift,huonw/swift,JaSpa/swift,ahoppen/swift,glessard/swift,sschiau/swift,djwbrown/swift,tinysun212/swift-windows,benlangmuir/swift,parkera/swift,kstaring/swift,CodaFi/swift,felix91gr/swift,ben-ng/swift,amraboelela/swift,huonw/swift,brentdax/swift,KrishMunot/swift,shajrawi/swift,swiftix/swift,harlanhaskins/swift,dduan/swift,manavgabhawala/swift,practicalswift/swift,hughbe/swift,natecook1000/swift,gmilos/swift,tardieu/swift,codestergit/swift,milseman/swift,jmgc/swift,manavgabhawala/swift,johnno1962d/swift,return/swift,kperryua/swift,IngmarStein/swift,kperryua/swift,austinzheng/swift,brentdax/swift,tinysun212/swift-windows,dduan/swift,felix91gr/swift,gribozavr/swift,jtbandes/swift,devincoughlin/swift,tinysun212/swift-windows,xedin/swift,jmgc/swift,CodaFi/swift,gottesmm/swift,dduan/swift,ben-ng/swift,allevato/swift,jckarter/swift,OscarSwanros/swift,shahmishal/swift,gribozavr/swift,tardieu/swift,gribozavr/swift,shahmishal/swift,austinzheng/swift,apple/swift,deyton/swift,stephentyrone/swift,return/swift,karwa/swift,frootloops/swift,JaSpa/swift,ken0nek/swift,codestergit/swift,hooman/swift,natecook1000/swift,frootloops/swift,bitjammer/swift,hughbe/swift,therealbnut/swift,uasys/swift,kstaring/swift,CodaFi/swift,jckarter/swift,zisko/swift,amraboelela/swift,hughbe/swift,practicalswift/swift,gregomni/swift,zisko/swift,milseman/swift,gmilos/swift,austinzheng/swift,KrishMunot/swift,djwbrown/swift,amraboelela/swift,devincoughlin/swift,stephentyrone/swift,zisko/swift,parkera/swift,ken0nek/swift,natecook1000/swift,glessard/swift,aschwaighofer/swift,JGiola/swift,return/swift,harlanhaskins/swift,felix91gr/swift,tkremenek/swift,zisko/swift,SwiftAndroid/swift,tinysun212/swift-windows,Jnosh/swift,swiftix/swift,allevato/swift,danielmartin/swift,shajrawi/swift,felix91gr/swift,hughbe/swift,nathawes/swift,austinzheng/swift,natecook1000/swift,nathawes/swift,benlangmuir/swift,aschwaighofer/swift,ken0nek/swift,codestergit/swift,roambotics/swift,manavgabhawala/swift,tjw/swift,nathawes/swift,ahoppen/swift,nathawes/swift,parkera/swift,sschiau/swift